Recent radio communication environment has been faced with the problem of rapid increase in data traffic. Thus, in 3GPP, such traffic is considered to be dispersed by increasing the density in a network in which a plurality of small cells are placed in a macro cell as disclosed in Non-Patent Literature 1 mentioned below. The technique of using such small cells is known as small cell enhancement. In the proposal of the 5G wireless communication scheme, an ultra-high density network (ultra-dense network) using a higher frequency and broader band than the existing network as disclosed in Non-Patent Literature 2 mentioned below is expected to be introduced.
The small cells are concepts that can include various kinds of cells (e.g. femtocell, nanocell, picocell, and microcell), which are arranged to be overlapped with the macro cell, smaller than the macro cell. In one example, the small cells are operated by a dedicated base station. In another example, the small cells are operated by allowing a terminal serving as a master device to operate temporarily as a small-cell base station. The so-called relay node can also be considered as a form of the small-cell base station. In the environments in which such small cells are operated, efficient use of radio resources and provision of low cost devices are important aspects.
The small-cell base station typically relays traffic between a macro-cell base station and a terminal. A link between the small-cell base station and the macro-cell base station is referred to as a backhaul link. Additionally, a link between the small-cell base station and a terminal is referred to as an access link. When the backhaul link is a radio link, by operating a radio backhaul link and an access link in a time division scheme, radio signals from these links can be prevented from interfering with each other.